Lead-acid batteries are still the main economic alternative as electric sources in most cars, trucks, buses, tractors, and motorcycles. They are used in boats, planes, submarines, electric cars, forklifts, luggage and other transportation, wheelchairs, golf and similar carts, as well as backup power supplies for telephone and computer centers, in telecommunications, in electrical power stations, in alarm and security systems, in load leveling, in emergency lights, as uninterrupted power supplies in case of power failure and during emergencies, for solar power generated electricity storage, and elsewhere.
The electromotive force in the lead acid battery is generated in the comproportionation redox reaction between lead (oxidation state 0) and lead dioxide (oxidation state 4) in aqueous sulfuric acid, resulting in lead sulfate (oxidation state 2), while consuming sulfuric acid. Beside several kilograms lead, the batteries contain additional toxic metals and sulfuric acid as the electrolyte, which makes their production and disposal one of the gravest economic and environmental problems, as there are two billion cars and trucks worldwide. Therefore, much efforts have been successfully exerted on developing technologies for recycling lead from used batteries. Not less important would be to reuse the batteries or to extend their life-span, but these efforts have been less successful.
The redox reaction product, lead sulfate, which accumulates during the production of the electrical current, covers the plates and reduces the surface of the reactive materials, lowering the voltage and the capacity of the battery, increasing the cell internal resistance. The process, called sulfation, leads to expanding sulfate deposits, to undesired crystallization of the amorphous deposit, to prolonging charging times while achieving only incomplete charging, to increasing charging temperatures, to loosening debris from plates to sediments, and it may lead to short-circuiting the cell or cracking the plates, and eventually to destroying the battery. When recharging the battery, while replenishing the consumed sulfuric acid, the lead sulfate should be ideally completely returned to the reactive components by the reverse—disproportionation—reaction, but a part of the material is never returned to lead and lead dioxide during repeated discharging and recharging. Therefore, a lead-acid battery has a limited life-span of several years, usually between two and five years.
There are physical techniques aiming at reversing the sulfation process, at least partially, by employing various regimens of electric treatments, and restoring some capacity, but the effects are quite limited. There have also been attempts to affect the battery ageing by the use of chemical additives in the electrolyte. U.S. Pat. No. 5,945,236 describes a mixture of sulfates, comprising toxic heavy metals, as an additive to extend a battery life, the additive being added in an amount of 20 grams per 1 kg lead. U.S. Pat. No. 7,160,645 relates to prolonging the battery life by adding to the electrolyte a mixture of lignin and a polymer like PVA together with a heavy metal salt.
It is an object of this invention to provide a nontoxic and environmentally safe additive to the electrolyte of lead acid battery for extending a useful life-span of the battery.
It also an object of this invention to provide an additive to the electrolyte of lead acid battery excluding heavy metals.
It is another object of this invention to provide an additive to the electrolyte of lead acid battery for improving the battery performance.
It is a further object of this invention to provide an additive to the electrolyte of lead acid battery to be used in refilling and regenerating a used battery.
It is a still further object of this invention to provide a method for extending the useful life of lead acid battery, comprising admixing into the electrolyte of said battery an additive without heavy metals.
Other objects and advantages of present invention will appear as description proceeds.